There is a known correction method of improving the precision of authentication by correcting image data including characteristic line information (e.g., fingerprints or palm prints, finger veins, palm veins, vascular patterns) that is used for the authentication. For example, local correction for correcting image data using local information and global correction for correcting image data using global information are known.
Specifically, with the local correction, an apparatus performs correction, for each region of the image data, on characteristic line information contained in a region using characteristic line information that is contained in a neighboring region. The correction is performed by using, for example, a smoothing filter. With the global correction, an apparatus performs correction using line information contained in a larger region than a neighboring region. The correction is performed by using, for example, modeling using a formula.
However, with the conventional methods described above, there is a problem in that, depending on the quality of the image that is used for the authentication, optimum correction cannot be obtained.
For example, with the local correction described above, because noise that is larger than a smoothing filter cannot be corrected, the correction is not suitable for an image that contains a large amount of noise. Furthermore, with the global correction described above, for example, because detailed line information cannot be maintained in accordance with a correction process, the correction is not suitable for a high quality image, which does not contain a large amount of noise.    Patent Document 1: International Publication Pamphlet No. WO 2005/086091 (Page 13 and FIG. 5)    Patent Document 2: Japanese Laid-open Patent Publication No. 2006-72553 (Pages 1 to 5 and FIG. 1)    Patent Document 3: Japanese Laid-open Patent Publication No. 10-334237 (Pages 1 to 8 and FIG. 1)    Patent Document 4: Japanese Laid-open Patent Publication No. 5-181956 (Pages 1 to 4 and FIG. 1)    Patent Document 5: Japanese Laid-open Patent Publication No. 9-62836 (Pages 1 to 3 and FIG. 1)